Turbine valve chest and nozzle plate construction

ABSTRACT

A small steam turbine with a separate external bolted-on valve chest is arranged to support an internally mounted nozzle box with an adjustable nozzle plate. The valve chest, nozzle box and nozzle plate are manufactured as a sub-assembly and attached to the turbine casing as a separate unit. The nozzle plate can subsequently be adjusted for concentric alignment with the firststage turbine buckets to compensate for accumulated dimensional variations due to manufacturing tolerances.

Waite Sttes tet [1 1 Price et a1.

1 Sept. 11, 1973 TURBINE VALVE CHEST AND NOZZLE PLATE CONSTRUCTEON [75]Inventors: Philip N. Price, Leominster; Herbert N. Hofitman, Lunenburg,both of Mass.

[73] Assignee: General Electric Company,

Schenectady, N.Y.

[22] Filed: Nov. 19, 1971 [21] Appl.No.:200,305

[52] 11.5. Cl. 415/217, 415/219 [5 l] Int. Cl F031) 1/04 [58] Field ofSearch 415/217-219, 201

[56] References Cited UNITED STATES PATENTS Junggren 415/218 2,848,1918/1958 Sachs et al 415/217 3,131,642 5/1964 Geer et a1. 415/201 PrimaryExaminerC. J. Husar Att0rneyWilliam C. Crutcher et al.

[57] ABSTRACT A small steam turbine with a separate external boltedonvalve chest is arranged to support an internally mounted nozzle box withan adjustable nozzle plate. The valve chest, nozzle box and nozzle plateare manufactured as a sub-assembly and attached to the turbine casing asa separate unit. The nozzle plate can subsequently be adjusted forconcentric alignment with the first-stage turbine buckets to compensatefor accumulated dimensional variations due to manufacturing tolerances.

4 Claims, 3 Drawing Figures PATENTEDSEPI 1191s FIG.2

TURBINE VALVE CHEST AND NOZZLE PLATE CONSTRUCTION BACKGROUND OF THEINVENTION This invention relates generally to an improved constructionfor small steam turbines of the type having external valve chestsseparately attached to the upper halves of the turbine casings andutilizing a multiplicity of steam control valves arranged for sequencialopening, and more particularly relates to more economical constructionsof such turbines.

. In the past, the nozzle plate, an arcuate member with an arcuate rowof ports which admit steam from the stationary part of such a turbine tothe rotating turbine buckets, has been attached to or located withrespect to the turbine casing. Therefore, since the rotating turbinebuckets are also carried on a rotor mounted within the casing, alignmentbetween these two elements which are mounted on a common member wasfairly simple. However, this approach required accurate machining of thecasing which did not lend itself to economical mass production of thesmaller types of steam turbines. Another disadvantage of prior artconstructions where the passages supplying the nozzle plate wereintegral with the turbine casing was that large'parts of the casing wereexposed to inlet steam conditions and had to be made of alloys whichcould withstand these conditions. I

It is, of course, known in the art to provide a separate valve chestcontaining sequentially actuated control valves admitting steam throughvalve seats to the individual turbine nozzle arcs. In some cases, thevalve chest is manufacturedas an'integral unit with the nozzle box andthis sub-assembly is bolted or otherwise attached to the turbine casing.The nozzle box does not need to be accurately aligned with the inlet tothe nozzle plate. However, the outlets from the nozzle plate, do need tobe accurately aligned with respect to the rotating buckets, and hence,the nozzle plate is generally supported from the casing itself ataccurately determined locations. Previously known methods for doing thishave been confined to machines requiring smaller nozzle arcs. It hasbeen previously suggested, as exemplified in U.S. Pat. No. 1,118,352 toJunggren, to support an arcuate nozzle plate of T-shaped cross sectionby means of two arcuate bolted-on segments. However, these members arenot adjustable and are disposed in machined grooves closely located withrespect to the tarbine casing.

Accordingly, one object of the present invention is to provide a moreeconomical construction in steam turbines with a separately attachedvalve chest accurately locating the nozzle ports with respect to theturbine buckets.

Another object of the invention is to provide an improved constructionfor a 'valve chest, nozzle box and nozzle plate sub-assembly whichprovides for adjustment due to accumulated dimensional tolerances.

SUMMARY OF THE INVENTION DRAWING The subject matter which is regarded asthe invention is particularly pointed out and distinctly claimed in theconcluding of the specification. The invention, however, both as toorganization and method of practice, together with further objects andadvantages thereof, may best be understood by reference to the followingdescription taken in connection with the accompanying drawing in which:

FIG. I is an elevation drawing, partly in section, of the inlet portionof a steam turbine;

FIG. 2 is an enlarged cross-sectional view of the adjustable nozzleplate and nozzle box attachment; and

FIG. 3 is an end view of the nozzle plate and attaching means shown inFIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 of thedrawing, portions are shown of the inlet portion of a turbine casing 1in which is disposed a rotor having turbine wheels with buckets mountedthereon, the first-stage wheel being indicated at 2 and buckets at 2a.The rest of the turbine casing (not shown) is of conventionalconstruction and the details are not material to the present invention.

Mounted on top of casing 1 is a separately attached valve chest 3likewise of conventional construction and held in place by a ring ofbolts 4. Valve chest 3 is typically elongated and is shown here in endview,there conventionally being a row of control valves 5 actuated in.sequence by a lift bar and control mechanism not pertinent to thepresent invention.

In accordance with the present invention, the valve chest 3 has anextending ledge 6 on its underside to which is attached a separatenozzle box or nozzle chest 7 by means of a ring of internal bolts 8. Thenozzle box Referring to FIG. 2 of the drawing, the nozzle plate 11 isseen to be ,of T-shaped cross section withupper and lower flanges 13',14, respectively. Outer and inner arcuate ring segments 15, 16 serve toclamp the respective flanges 1 3, 14 to the' nozzle box by means ofbolts 17. Top and bottom flanges l3, 14 are provided with oversizedholes 18 accommodating the shanks 17a of bolts 17 so that the nozzleplate 11 can he slid to the desired position onthe face of nozzle box 7before clamping in placeJDowel pins 19 drilled after final assembly andalignment then locate the nozzle plate 11 with respect to the inner ringsegment 16.

Reference to FIG. 3 of the drawing. showing an end view illustrates thelocation of the bolts 17 on the inner and outer ring segments 15, 16.Also, the locations of the two locating dowels 19 areindicatedrReference to the right-hand side of FIG. 3 shows how thegenerous clearance of holes 18 in the nozzle plate flanges around thebolt shanks will permit sliding the nozzle plate to the final desiredlocation. As indicated on the lefthand side of FIG. 3, the inner ringsegment 16 is located with respect to the nozzle box by bolts 17 and thefinal assembly placement of dowels 19 then locates the nozzle plate 11with respect to the inner segment.

OPERATION OF THE INVENTION Operation of the invention will be made moreclear by reference first to FIG. 1. The first source of possiblevariation due to manufacturing tolerances is the juncture of casing 1with valve chest 3. The next source of possible variance is at thejuncture of valve chest 3 with nozzle box 7. A third source of varianceis due to variation of the rotor location with respect to the casing andvariations in manufacture of turbine wheel 2 which ultimately affectsthe location of turbine buckets 2a. Thus, an accumulation of otherwiseacceptable manufacturing tolerances for each separate piece could placethe nozzle ports 12 substantially out of alignment with turbine buckets2a. These accumulated tolerances are compensated for by movement of thenozzle plate 11 by means of the adjustable fastening arrangementindicated in FIGS. 2 and 3. Therefore, using the present invention, thevarious units such as the valve chest 3, nozzle box 7, and nozzle plate11 may be manufactured from the most economical alloys which meet theservice requirements for each separate part. Then they 1 may bepreassembled as a sub-assembly and attached to the turbine at asubsequent time, all of the foregoing leading to reduced cost ofmanufacture.

While there has been described what is considered to be the preferredembodiment of the invention, other modifications may occur to thoseskilled in the art and it is intended to cover in the appended claimsall such modifications as fall within the true spirit and scope of theinvention.

What is claimed is:

1. In a steam turbine having a casing with a rotor carrying acircumferential row of axial flow turbine buckets, the improvementcomprising:

a separate valve chest detachably connected to said casing,

a separate nozzle box detachably connected to said valve chest anddefining at least one arcuate surface spaced from said buckets andhaving openings in said surface communicating with said valve chest,

an arcuate nozzle plate mounted -on said nozzle box surface and havingnozzle passages communicating between said nozzle box openings andbuckets, and

fastening means connecting said nozzle plate to said nozzle box andarranged to permit relative adjust ment therebetween so as to align saidnozzle passages accurately with the buckets.

2. The combination according to claim 1, wherein said nozzle plateincludes outer and inner arcuate flanges having enlarged holes therein,and wherein said fastening means comprises at least one arcuate ringsegment disposed over one of said flanges together with bolts clampingthe flange'between the ring segment and the nozzle box,the bolt shanksproviding substantial clearance inside said enlarged holes to providefor adjustment of the nozzle plate.

3. The combination according to claim 2, and further including dowelmeans joining said ring segment and said flange for accurately locatingthe nozzle plate after final adjustment.

4. In a steam turbine having a casing with a rotor carrying acircumferential row of axial flow turbine buckets, the improvementcomprising:

a separate valve chest detachably connected to said casing,

a separate nozzle box detachably connected to said valve chest anddefining at least one arcuate surface spaced from said buckets and alsohaving openings communicating with said valve chest,

an arcuate nozzle plate having a T-shaped cross section with outer andinner arcuate flanges mounted on said nozzle box surface and having aplurality of nozzle passages communicating between said nozzle boxopenings and the buckets,

outer and inner ring segments disposed over said respective outer andinner flanges,

a plurality of bolts passing through said ring segments and flanges intothe nozzle box for clamping the nozzle plate to the nozzle box, theholes in the nozzle plate flanges being enlarged to provide clearancearound said bolts for adjustment of the nozzle plate, and

dowel means joining one of said ring segments to a nozzle plate flangeso as to locate the nozzle plate with respect to said buckets subsequentto final assembly.

1. In a steam turbine having a casing with a rotor carrying acircumferential row of axial flow turbine buckets, the improvementcomprising: a separate valve chest detachably connected to said casing,a separate nozzle box detachably connected to said valve chest anddefining at least one arcuate surface spaced from said buckets andhaving openings in said surface communicating with said valve chest, anarcuate nozzle plate mounted on said nozzle box surface and havingnozzle passages communicating between said nozzle box openings andbuckets, and fastening means connecting said nozzle plate to said nozzlebox and arranged to permit relative adjustment therebetween so as toalign said nozzle passages accurately with the buckets.
 2. Thecombination according to claim 1, wherein said nozzle plate includesouter and inner arcuate flanges having enlarged holes therein, andwherein said fastening means comprises at least one arcuate ring segmentdisposed over one of said flanges together with bolts clamping theflange between the ring segment and the nozzle box,the bolt shanksproviding substantial clearance inside said enlarged holes to providefor adjustment of the nozzle plate.
 3. The combination according toclaim 2, and further including dowel means joining said ring segment andsaid flange for accurately locating the nozzle plate after finaladjustment.
 4. In a steam turbine having a casing with a rotor carryinga circumferential row of axial flow turbine buckets, the improvementcomprising: a separate valve chest detachably connected to said casing,a separate nozzle box detachably connected to said valve chest anddefining at least one arcuate surface spaced from said buckets and alsohaving openings communicating with said valve chest, an arcuate nozzleplate having a T-shaped cross section with outer and inner arcuateflanges mounted on said nozzle box surface and having a plurality ofnozzle passages communicating between said nozzle box openings and thebuckets, outer and inner ring segments disposed over said respectiveouter and inner flanges, a plurality of bolts passing through said ringsegments and flanges into the nozzle box for clamping the nozzle plateto the nozzle box, the holes in the nozzle plate flanges being enlargedto provide clearance around said bolts for adjustment of the nozzleplate, and dowel means joining one of said ring segments to a nozzleplate flange so as to locate the nozzle plate with respect to saidbuckets subsequent to final assembly.